Voltammetric reduction of strong polyprotic acids in solutions with excess and without supporting electrolyte was studied both theoretically and experimentally. A theoretical model based on the transport (diffusion and migration) equations and the electroneutrality principle was used to compute voltammograms by finite difference simulation under both steady state and transient conditions. Simulated voltammograms are compared with experimental reduction curves obtained at platinum microelectrodes without and with excess electrolyte for two strong polyprotic acids, sulfuric (H2SO4) and tungstosilicic (H4W12SiO40) acids. Perchloric acid (HClO4) was used as the reference for comparison. The experimental results agree well with the calculated voltammetric curves both without and with excess supporting electrolyte. The dependence of voltammetric response on the concentration of acids is also discussed.